Parallel vertical recirculating gantry system

ABSTRACT

Disclosed are various embodiments for a vertically recirculating gantry system operating in parallel with multiple actuators on multiple gantries. A plurality of items are retrieved from a plurality of picking locations via a plurality of actuators disposed on a gantry spanning a width of the plurality of conveyors. The gantry is moved along a track toward a plurality of stowage locations. Individual items are deposited in respective stowage locations via the plurality of actuators as the gantry moves over the stowage locations.

BACKGROUND

A significant task in materials handling facilities involves sortationof items. Items are shipped to various destinations, and it is importantto group items together that are being shipped to a common destinationor via a common transport. For instance, items may be grouped togetheron a pallet for shipment. Current approaches for sortation are burdenedwith high amounts of manual sortation labor. Manual sortation is slow,expensive, and likely to result in errors.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present disclosure can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale, with emphasis instead being placed uponclearly illustrating the principles of the disclosure. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a drawing of a perspective view of a vertically recirculatinggantry system according to one embodiment of the present disclosure.

FIG. 2A is a drawing of a side view of the vertically recirculatinggantry system of FIG. 1 according to one embodiment of the presentdisclosure.

FIG. 2B is a drawing of a lengthwise view of a gantry employed in thevertically recirculating gantry system of FIG. 1 according to oneembodiment of the present disclosure.

FIG. 3 is a drawing of an overhead view of the vertically recirculatinggantry system of FIG. 1 according to one embodiment of the presentdisclosure.

FIG. 4 is a drawing of a perspective view of a horizontallyrecirculating gantry system according to one embodiment of the presentdisclosure.

FIG. 5 is a drawing of a side view of the horizontally recirculatinggantry system of FIG. 4 according to one embodiment of the presentdisclosure.

FIG. 6A is a drawing of an overhead view of the horizontallyrecirculating gantry system of FIG. 4 according to one embodiment of thepresent disclosure.

FIG. 6B is a drawing of a perspective view of a vertically recirculatinggantry system using a rollercoaster-style track according to oneembodiment of the present disclosure.

FIG. 7 is a drawing of a perspective view of a horizontallyrecirculating gantry system with multiple sets of conveyors and itemstorage locations according to one embodiment of the present disclosure.

FIG. 8 is a drawing of a perspective view of the verticallyrecirculating gantry system of FIG. 1 that illustrates rotation of itemstorage locations according to one embodiment of the present disclosure.

FIG. 9 is a schematic block diagram of a networked environment accordingto various embodiments of the present disclosure.

FIG. 10 is a flowchart illustrating one example of functionalityimplemented as portions of a gantry system according to variousembodiments of the present disclosure.

FIG. 11 is a flowchart illustrating one example of functionalityimplemented as portions of a gantry system control application executedin a computing environment in the networked environment of FIG. 9according to various embodiments of the present disclosure.

FIG. 12 is a schematic block diagram that provides one exampleillustration of a computing environment employed in the networkedenvironment of FIG. 9 according to various embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure relates to recirculating gantry systems forsortation of items in a materials handling facility, such as awarehouse, distribution center, cross-docking facility, or fulfillmentcenter. Current approaches to sortation of items and building up palletsare highly labor intensive. For instance, workers may manually retrieveitems, determine a destination pallet, and then manually place the itemson the pallet to build up the pallet. The workers may then use forkliftsor pallet dollies to move the finished pallets around the materialshandling facility. Such approaches have slow throughput, are costly interms of manual labor, and are likely to result in human-caused errors.

Various embodiments of the present disclosure introduce recirculatinggantry systems that can sort items and build pallets in an automatedway, thereby increasing throughput while reducing costs and errors.Items such as boxes, containers, bubble-wrapped flats, and so forth areautomatically routed to one of multiple parallel picking locations, suchas conveyors or pallets. The items are retrieved from the pickinglocations by one or more actuators on an overhead gantry supported formovement along a track and spanning the picking locations. The gantrymoves along the track in a first direction towards a series ofside-by-side stowage locations, such as pallets or conveyors, past theend of the picking locations. Where the stowage locations are pallets,the stowage locations may be multiple pallets deep in the firstdirection, such that several stowage locations are aligned with eachpicking location. Each actuator deposits its respective cargo on acorresponding stowage location as the gantry moves along the track overthe stowage location. Also, an actuator may move left or right along thegantry to deposit its item in a parallel stowage location. In this way,N items in N parallel picking areas can be retrieved and sorted througha single gantry pass into a respective set of M destinations per pickingarea, for a total of N×M possible destinations.

As will be described, the overhead gantries are capable of automatedrecirculation. In a first embodiment, the recirculation is vertical,where, after depositing the items in the stowage locations, the gantrymoves about a track having upper and lower runs that are spacedvertically from each other to return to the picking locations toretrieve another load of items. In a second embodiment, therecirculation is horizontal, where, after depositing the items in thestowage locations, the gantry moves about a horizontally oriented trackto return to the picking locations to retrieve another load of items. Ina variation on the second embodiment, the picking locations and stowagelocations may be mirrored on the opposite side of the horizontal tracksuch that the gantry arrives at another set of picking locations afterdropping off items in stowage locations. Also, in any embodiment,multiple gantries may operate simultaneously on the same track, suchthat after a first gantry retrieves a first set of items from thepicking locations and begins moving towards the stowage locations, asecond gantry following behind the first on the track retrieves a secondset of items from the picking locations, and so forth. In the followingdiscussion, a general description of the system and its components isprovided, followed by a discussion of the operation of the same.

Referring now to FIG. 1, shown is a perspective view of a verticallyrecirculating gantry system 100 according to one embodiment. Thevertically recirculating gantry system 100 is operable to sort anddistribute items 103 arriving via multiple picking locations 106 in apicking area to multiple stowage locations 109 in a stowage area. Inthis example, the picking locations 106 are conveyors, while the stowagelocations 109 are pallets. In other examples, stowage locations 109 maybe conveyors, etc., while picking locations 106 may be pallets, etc. Asthe items 103 arrive via the picking locations 106, vertically mountedrobots 112 may orient the items 103 on the picking locations 106 so asto be ready to be retrieved by the actuators 115. For example, thevertically mounted robots 112 may pick up items 103 via a mechanicalgrip or via suction applied through pneumatic pads and then rotate theitems 103 and/or move the items 103 left or right. Although multipleindependent picking conveyors are shown as the picking locations 106, inother scenarios a single conveyor with multiple lanes may be utilized.

The actuators 115 are disposed on a gantry 118 having a beam that spansthe width of the picking locations 106 and the stowage locations 109.The gantry 118 moves about a track 121 with an upper run 122 and a lowerrun 123, spaced vertically from each other, such that the gantry 118travels in a path over the stowage locations 109. After retrieving items103, the actuators 115 move via the gantry 118 over the stowagelocations 109 and then deposit the items 103 in respective stowagelocations 109. The actuators 115 may be vertically telescoping to reachinto the stowage locations 109 to deposit the items 103. After passingover the stowage locations 109, the gantry 118 and the actuators 115vertically recirculate about the track 121 in order to return to thepicking locations 106. The gantry 118 and actuators 115 invert andtravel back upside down.

As shown in FIG. 1, there may be multiple gantries 118 movingsimultaneously about the vertically oriented track 121. This creates aparallelized situation providing for exceptionally high throughput asitems are removed from the picking locations 106 through a single passof actuators 115 of one gantry 118, while items 103 are also beingdeposited in the stowage locations 109 by another gantry 118.

Turning now to FIG. 2A, shown is a side view of the verticallyrecirculating gantry system 100 of FIG. 1 according to one embodiment.As indicated by the arrows indicating direction of travel, the gantries118 (FIG. 1) and actuators 115 move in a counter-clockwise direction inthis example. At position 203, multiple actuators 115 are able tosimultaneously retrieve multiple items 103 from the side-by-side pickinglocations 106. The actuators 115 may use negative pressure or suction,electrostatic force, a mechanical grasp, or another approach to retrievethe items 103. In one embodiment, the gantry 118 includes a singlevacuum source that is operable to create suction at each of theactuators 115. After retrieving an item 103, an actuator 115 mayactivate a wire gripper underneath the item 103 that can open and closeto maintain a grip on the item 103 in the event of loss of power or amalfunction that otherwise releases the item 103. For example, when theitem 103 is picked up, the wire gripper may be open. Subsequently, awire or other mechanical support can close in to secure the item 103mechanically.

As the actuators 115 retrieve the items 103, identifiers on the items103 may be scanned, and specific destination stowage locations 109 maybe determined for the items 103. As shown in FIG. 2A, three stowagelocations 109 a, 109 b, and 109 c are arranged in a line with thepicking location 106. The actuator 115 may deposit an item 103 in anyone of the stowage locations 109 a, 109 b, or 109 c, thereby sorting theitem 103 to an appropriate destination. As shown, the actuator 115 mayvertically telescope downward to place the item 103 appropriately withina selected item storage location 109 a.

Continuing to FIG. 2B, shown is a drawing of a lengthwise view of agantry 118 employed in the vertically recirculating gantry system 100(FIG. 1) according to one embodiment. As shown in this example, thegantry 118 has eight actuators 115, but more or fewer actuators 115 maybe used in other examples. The actuators 115 are capable of lateralmovement along the gantry 118, either through motors in the individualactuators 115 or attachment of the actuators 115 to a drive cable, belt,etc. that facilitates movement along the gantry 118.

Also, the actuators 115 are capable of moving up and down, via avertically telescoping arm 209. In this example, one or more pneumaticpads 212 are attached at the bottom of the actuator 115 in order toapply vacuum force to grab and retain an item 103 from a pickinglocation 106 (FIG. 2) and deposit the item 103 into a stowage location109 (FIG. 2). A wire gripper may be used underneath the item 103 toretain the item 103 in the event of loss of vacuum suction.

In various embodiments, the gantry 118 itself may be capable oftelescoping horizontally in order to extend the reach of the actuators115 by allowing for additional lateral movement. This would increase ordecrease the footprint of what items 103 can be reached via the system,thereby potentially increasing or decreasing the system's throughput.

In various embodiments, the actuators 115 may be capable of one or moredegrees of freedom. As discussed, actuators 115 may move side-to-side ona gantry 118 or up-and-down via the vertically telescoping arm 209. Anactuator 115 may also move in various embodiments via a rotation axis orin combinations to create screw motions (i.e., rotation coupled withtranslation). Also, in some embodiments, multiple actuators 115 mayfunction collaboratively. For example, two actuators 115 may assist inretrieving and/or depositing a single item 103. Where actuators 115 ongantries 118 are retrieving items 103 from conveyors, the use ofmultiple recirculating gantries 118 may allow the actuators 115 to pickthe items 103 from the conveyors while matching the speed of theconveyors.

Moving on to FIG. 3, shown is an overhead view of the verticallyrecirculating gantry system 100 of FIG. 1 according to one embodiment.As indicated by the directional arrows on FIG. 3, an actuator 115 may becapable of lateral movement along the gantry 118. This lateral movementmay be limited due to the presence of multiple actuators 115 on the samegantry 118. As shown in this example, a given actuator 115 may be movedleft by one position or may be moved right by one position in order todeposit an item 103 in any one of the rows 303 a, 303 b, or 303 c ofstowage locations 109 a, 109 b, or 109 c that may be in line with theparallel picking locations 106.

Also, FIG. 3 illustrates that the gantries 118 may be supported on theends by the tracks 121 a and 121 b. This is merely by way of example, asother number of tracks 121 may be used at differing positions forsupporting the gantries 118. In one example, the tracks 121 may includegearing that drives the gantries 118 along the tracks 121.

With reference to FIG. 4, shown is a perspective view of a horizontallyrecirculating gantry system 400 according to one embodiment. In contrastto the vertically recirculating gantry system 100 depicted in FIGS. 1-3,the horizontally recirculating gantry system 400 includes one or moregantries 118 that move about a horizontally oriented track 403. In oneexample, the horizontally oriented track 403 may comprise arollercoaster-style track, which may be oval in shape or another shape.As shown, the gantries 118 may be centered on the horizontally orientedtrack 403. In various examples, the gantries 118 may be mounted above orbelow the horizontally oriented track 403. In one implementation, thegantries 118 may be propelled along the horizontally oriented track 403using magnetic levitation technology.

As with the vertically recirculating gantry system 100, the horizontallyrecirculating gantry system 400 is operable to retrieve items 103 fromthe picking locations 106 via actuators 115 disposed on the gantries118, and then to move the gantries 118 about the horizontally orientedtrack 403 toward the stowage locations 109. When passing over particularstowage locations 109, the actuators 115 can deposit their cargo in thestowage locations 109. Afterward, the gantries 118 continue along thehorizontally oriented track 403 to return to the picking locations 106to retrieve additional items 103. The horizontally oriented track 403may be designed such that the returning gantries 118 do not interferewith or overlap the other gantries 118 that are moving items 103.

Continuing to FIG. 5, shown is a side view of the horizontallyrecirculating gantry system 400 of FIG. 4 according to one embodiment.The arrow indicates the direction of travel of the gantries 118 alongthe horizontally oriented track 403. It is noted that the gantries 118and actuators 115 do not vertically invert in this embodiment, unlikethe vertically recirculating gantry system 100 of FIG. 1.

Moving on to FIG. 6A, shown is an overhead view of the horizontallyrecirculating gantry system 400 of FIG. 4 according to one embodiment.The arrow indicates the direction of travel of the gantries 118 alongthe horizontally oriented track 403 in a counter-clockwise direction,though the position of the picking locations 106 and the stowagelocations 109 may be inverted in other embodiments, resulting in anopposite direction of travel.

Turning now to FIG. 6B, shown is a perspective view of a verticallyrecirculating gantry system 600 using a rollercoaster-style track 603according to one embodiment. Unlike the track 403 of FIGS. 4-6A, thetrack 603 is oriented for vertical recirculation. In particular, thetrack 603 includes an upper run 606 and a lower run 609 spacedvertically from each other. After the gantry 118 moves over the stowagelocations 109, the gantry 118 continues on the track 603, verticallyinverts, and then recirculates back to the pickup locations 106.

With reference to FIG. 7, shown is a perspective view of a horizontallyrecirculating gantry system 700 according to one embodiment. As comparedwith the horizontally recirculating gantry system 400 of FIG. 4, theremay be multiple sets of picking areas 703 a and 703 b and multiple setsof stowage areas 706 a and 706 b. In the example of FIG. 7, the sets ofpicking areas 703 and stowage areas 706 are mirrored on opposite sidesof the horizontally oriented track 403.

The gantries 118 in this example travel in a clockwise direction aboutthe horizontally oriented track 403. After retrieving items 103 frompicking area 703 a and depositing them in stowage area 706 a, thegantries 118 and actuators 115 next retrieve items 103 from picking area703 b and deposit them in stowage area 706 b, before recirculating aboutthe horizontally oriented track 403 to return to the picking area 703 a.

Depending on the size of the horizontally oriented track 403, any numberof sets of picking areas 703 and stowage areas 706 may be provided. Inaddition, the vertically recirculating gantry system 100 may includemultiple sets of picking areas 703 and stowage areas 706 arrangedlinearly along the track 121 (FIG. 1). However, the multiple sets ofpicking areas 703 and stowage areas 706 may be particularly beneficialwith respect to a horizontally oriented track 403 due to the spacenecessary to accommodate the horizontally oriented track 403.

Turning now to FIG. 8, shown is a perspective view of the verticallyrecirculating gantry system 100 of FIG. 1 that illustrates rotation ofstowage locations 109 according to one embodiment. The same principlesmay apply to the horizontally recirculating gantry systems 400 (FIG. 4)and 700 (FIG. 7). Each of the stowage locations 109 is occupied by arespective storage unit 803. Each storage unit 803 comprises a gaylord806 disposed on top of a pallet 809, thereby surrounding or enclosing avolume above the pallet 809. Each pallet 809 in turn sits above a pod812 configured to accommodate a robotic drive unit 815.

In one preferred embodiment, robotic drive units 815 are utilized inorder to move storage units 803 in and out of stowage locations 109. Forexample, as shown in FIG. 8, a storage unit 803 a is being moved out ofan item storage location 109 by a robotic drive unit 815, while astorage unit 803 b is being moved into the item storage location 109 bya robotic drive unit 815. The storage units 803 may be moved away whenthey are determined to meet a capacity threshold in terms of volume,weight, or other factors. Alternatively, the storage units 803 may bemoved away when it is determined that further items 103 are not to besent to the common destination. An empty storage unit 803 may be movedin to replace the full storage unit 803. After the storage unit 803 ismoved away, the gaylord 806 may be removed, and the pallet 809 bearingthe items 103 may be wrapped or otherwise packaged. In otherembodiments, the storage units 803 may be moved in and out manually viaa dolly or forklift.

While the storage units 803 are being moved in and out, the operation ofthe vertically recirculating gantry system 100 may be temporarilypaused. Where possible, the vertically recirculating gantry system 100may be configured to assign items 103 to alternate stowage locations109, thereby avoiding interference with the particular storage units 803a and 803 b being moved out and in, respectively. For example, any items103 present on the conveyors that are to be stowed on a pallet or in alocation not currently positioned in the stowage area may remain on theconveyors until the stowage location is ready to receive the items 103.

With reference to FIG. 9, shown is a networked environment 900 accordingto various embodiments. The networked environment 900 includes acomputing environment 903, one or more gantry controllers 906, one ormore robotic drive unit controllers 909, one or more orienting robotcontrollers 912, one or more actuator controllers 915, and one or moreconveyor controllers 918, which are in data communication via a network921. The network 921 includes, for example, the Internet, intranets,extranets, wide area networks (WANs), local area networks (LANs), wirednetworks, wireless networks, cable networks, satellite networks, orother suitable networks, etc., or any combination of two or more suchnetworks.

The computing environment 903 may comprise, for example, a servercomputer or any other system providing computing capability.Alternatively, the computing environment 903 may employ a plurality ofcomputing devices that may be arranged, for example, in one or moreserver banks or computer banks or other arrangements. Such computingdevices may be located in a single installation or may be distributedamong many different geographical locations. For example, the computingenvironment 903 may include a plurality of computing devices thattogether may comprise a hosted computing resource, a grid computingresource, and/or any other distributed computing arrangement. In somecases, the computing environment 903 may correspond to an elasticcomputing resource where the allotted capacity of processing, network,storage, or other computing-related resources may vary over time.

Various applications and/or other functionality may be executed in thecomputing environment 903 according to various embodiments. Also,various data is stored in a data store 924 that is accessible to thecomputing environment 903. The data store 924 may be representative of aplurality of data stores 924 as can be appreciated. The data stored inthe data store 924, for example, is associated with the operation of thevarious applications and/or functional entities described below.

The components executed on the computing environment 903, for example,include a gantry system control application 927 and other applications,services, processes, systems, engines, or functionality not discussed indetail herein. The gantry system control application 927 is executed toorchestrate control of the operation of a gantry system, such as thevertically recirculating gantry system 100 or the horizontallyrecirculating gantry system 400 or 700. The gantry system controlapplication 927 may be a part of a larger system that orchestratessortation of items 103 that are inbound to or outbound from a materialshandling facility.

The data stored in the data store 924 includes, for example, systemstate 930, item data 933, storage unit data 936, item-storage unitassignment data 939, and potentially other data. The system state 930records a current state of a gantry system, including operational statusof picking locations 106, actuators 115, and gantries 118, as well asstatus of stowage locations 109 and positions of storage units 803. Theitem data 933 includes various information about items 103 beingprocessed by the gantry system, including, for example, weight,dimensions, destination, fragility or hazardous characteristics, and soforth.

The storage unit data 936 includes various information about storageunits 803 being loaded via the gantry system, including, for example,capacities, destinations, fragility or hazardous characteristics ofassigned items 103, current location in the materials handling facility,and so on. The item-storage unit assignment data 939 records theassignments of items 103 to storage units 803. These assignments mayhave already been implemented, or may be tentative (awaitingimplementation by the gantry system).

The gantry controllers 906 include circuitry configured to operategantries 118 about a track 121 or a horizontally oriented track 403. Thegantry controllers 906 may report a current position relative to a track121 or a horizontally oriented track 403. The gantry controllers 906 maybe commanded to move in a specified direction and at a specified speedalong a track 121 or a horizontally oriented track 403. In someembodiments, the gantries 118 may be controlled via a common drivemechanism. For example, the gantries 118 may latch onto a moving cable.The gantries 118 on a single track 121 or horizontally oriented track403 may be independently operable, or multiple gantries 118 may operatein unison. Where the gantries 118 are horizontally telescoping, thegantry controller 906 may direct a gantry 118 to expand or contract,thereby changing the width of the gantry 118 as desired.

The robotic drive unit controllers 909 include circuitry configured tooperate robotic drive units 815 in the materials handling facility. Therobotic drive units 815 may be independently powered (e.g., via abattery) and may autonomously navigate the floor of the materialshandling facility.

The orienting robot controllers 912 include circuitry configured tooperate robots 112 in order to correctly orient incoming items 103 onpicking locations 106. The robots 112 may include sensors to detectcurrent positions of items 103 and actuators in order to move the items103 to correct positions. The correct positions are determined in orderto accommodate the incoming actuators 115 that will retrieve the items103.

The actuator controllers 915 include circuitry configured to operateactuators 115 on gantries 118. The actuator controllers 915 may reportcurrent status of the actuators 115, such as position on the gantries118, extension length, whether an item 103 is being conveyed, and soforth. The actuator controllers 915 may control lateral movement of theactuators 115 along the gantries 118, extension length of the actuators115, and whether the actuators 115 are applying force, vacuum grip,and/or other techniques to retrieve and transport items 103. Theactuator controllers 915 may control scanners 942 that scan identifierssuch as radio-frequency identifiers (RFIDs), barcodes, and/or otheridentifiers on the items 103 in order to identify the items 103.

The conveyor controllers 918 include circuitry configured to operate thepicking locations 106. The picking locations 106 may be turned on oroff, and the direction and/or speed of the operation may be adjusted.The conveyor controllers 918 may report the current status of thepicking locations 106.

Referring next to FIG. 10, shown is a flowchart that provides oneexample of the operation of a portion of a gantry system 1000corresponding to the vertically recirculating gantry system 100 of FIG.1 or the horizontally recirculating gantry system 400 of FIG. 4according to various embodiments. It is understood that the flowchart ofFIG. 10 provides merely an example of the many different types offunctional arrangements that may be employed to implement the operationof the portion of the gantry system 1000 as described herein. As analternative, the flowchart of FIG. 10 may be viewed as depicting anexample of elements of a method implemented in the computing environment903 (FIG. 9) according to one or more embodiments.

Beginning with box 1003, items 103 are deposited onto picking locations106 of the gantry system 1000, and the picking locations 106 areoperated by the conveyor controller(s) 918 to advance the items 103toward the robots 112. In box 1006, the robots 112 are operated by theorienting robot controllers 912 to orient the items 103 so as to be in acorrect orientation to be retrieved from the picking locations 106 bythe actuators 115.

In box 1009, the actuators 115 on a gantry 118 are operated via thegantry controllers 906 and the actuator controllers 915 to retrieve theitems 103 from the picking locations 106. In box 1012, the items 103 areidentified via scanning respective identifiers on the items 103 via thescanners 942 of the actuators 115. In box 1015, the gantry systemcontrol application 927 determines destination stowage locations 109 forthe identified items 103 according to the item-storage unit assignmentdata 939. The destination stowage locations 109 may be determinedaccording to a variety of factors including common shipping destination,fragility and/or hazardous characteristics, available capacity in astorage unit 803, possible stowage locations 109 that can be reached bythe corresponding actuator 115, and so forth.

In box 1018, the gantry 118 is moved via the gantry controller 906 alongthe track 121 or horizontally oriented track 403 toward the stowagelocations 109. In box 1021, the gantry system control application 927determines whether to move one or more actuators 115 laterally along thegantry 118. The actuators 115 may need to be moved left or right inorder to reach a particular item storage location 109 or to position theitem 103 within the particular stowage location 109. In some cases,moving one actuator 115 may require that another actuator 115 be movedin order to make room. If actuators 115 are to be moved laterally, theactuator controller(s) 915 effect the lateral movement along the gantry118 in box 1024. Otherwise, the flow proceeds to box 1027.

In box 1027, the gantry system control application 927 determineswhether the gantry 118 is over a particular destination stowage location109 for an item 103 currently held by an actuator 115. If so, theactuator controller 915 causes the item 103 to be deposited in the itemstorage location 109 in box 1030. If the gantry 118 is not over aparticular destination stowage location 109, the flow returns to box1018 and the gantry 118 continues movement along the track. It is notedthat a gantry 118 may have multiple actuators 115 operating in paralleland that items 103 may be deposited at different times and at differentstowage locations 109.

After all items 103 are deposited, in box 1033, the gantry 118 isrecirculated along the track to the picking locations 106. In someembodiments (e.g., the embodiment of FIG. 7), the gantry 118 mayrecirculate to a different set of picking locations 106 beforeretrieving another set of items 103 and depositing those items 103 to adifferent set of stowage locations 109. After this, the gantry 118 mayrecirculate to the original set of picking locations 106.

Referring next to FIG. 11, shown is a flowchart that provides oneexample of the operation of a portion of a gantry system controlapplication 927. It is understood that the flowchart of FIG. 11 providesmerely an example of the many different types of functional arrangementsthat may be employed to implement the operation of the portion of thegantry system control application 927 as described herein. As analternative, the flowchart of FIG. 11 may be viewed as depicting anexample of elements of a method implemented in the computing environment903 (FIG. 9) according to one or more embodiments.

Beginning with box 1103, the gantry system control application 927determines the current status of the storage units 803 at the stowagelocations 109. For example, the gantry system control application 927may determine which items 103 are stored and/or assigned to the storageunits 803, their weights, their dimensions, and so forth. In box 1106,the gantry system control application 927 determines whether a storageunit 803 meets, or is soon predicted to meet, a capacity threshold. Ifnot, the gantry system control application 927 returns to box 1103 andreassesses the current status in view of additional events.

If a storage unit 803 meets a capacity threshold, the gantry systemcontrol application 927 modifies the gantry system 1000 operation toaccommodate the change out of a storage unit 803 in box 1109. This mayinvolve pausing operation of portions of the gantry system 1000,redirecting items 103 to other stowage locations 109, allowing items 103to queue up on the picking locations 106, or other actions.

In box 1112, the gantry system control application 927 causes a firststorage unit 803 to move out from the stowage location 109. In thisregard, the gantry system control application 927 may direct a roboticdrive unit 815 to travel to the storage unit 803, lift the storage unit803, and transport the storage unit 803 away from the stowage location109.

In box 1115, the gantry system control application 927 causes a secondstorage unit 803 to move into the stowage location 109. The secondstorage unit 803 may be empty or may contain items 103. In this regard,the gantry system control application 927 may direct a robotic driveunit 815 to travel to the second storage unit 803, lift the secondstorage unit 803, and transport the storage unit 803 to the stowagelocation 109.

In box 1118, the gantry system control application 927 restoresoperation of the gantry system 1000 so that items 103 begin beingassigned to the stowage location 109 where the second storage unit 803is positioned. Thereafter, the operation of the portion of the gantrysystem control application 927 ends.

With reference to FIG. 12, shown is a schematic block diagram of thecomputing environment 903 according to an embodiment of the presentdisclosure. The computing environment 903 includes one or more computingdevices 1200. Each computing device 1200 includes at least one processorcircuit, for example, having a processor 1203 and a memory 1206, both ofwhich are coupled to a local interface 1209. To this end, each computingdevice 1200 may comprise, for example, at least one server computer orlike device. The local interface 1209 may comprise, for example, a databus with an accompanying address/control bus or other bus structure ascan be appreciated.

Stored in the memory 1206 are both data and several components that areexecutable by the processor 1203. In particular, stored in the memory1206 and executable by the processor 1203 are the gantry system controlapplication 927 and potentially other applications. Also stored in thememory 1206 may be a data store 924 and other data. In addition, anoperating system may be stored in the memory 1206 and executable by theprocessor 1203.

It is understood that there may be other applications that are stored inthe memory 1206 and are executable by the processor 1203 as can beappreciated. Where any component discussed herein is implemented in theform of software, any one of a number of programming languages may beemployed such as, for example, C, C++, C#, Objective C, Java®,JavaScript®, Perl, PHP, Visual Basic®, Python®, Ruby, Flash®, or otherprogramming languages.

A number of software components are stored in the memory 1206 and areexecutable by the processor 1203. In this respect, the term “executable”means a program file that is in a form that can ultimately be run by theprocessor 1203. Examples of executable programs may be, for example, acompiled program that can be translated into machine code in a formatthat can be loaded into a random access portion of the memory 1206 andrun by the processor 1203, source code that may be expressed in properformat such as object code that is capable of being loaded into a randomaccess portion of the memory 1206 and executed by the processor 1203, orsource code that may be interpreted by another executable program togenerate instructions in a random access portion of the memory 1206 tobe executed by the processor 1203, etc. An executable program may bestored in any portion or component of the memory 1206 including, forexample, random access memory (RAM), read-only memory (ROM), hard drive,solid-state drive, USB flash drive, memory card, optical disc such ascompact disc (CD) or digital versatile disc (DVD), floppy disk, magnetictape, or other memory components.

The memory 1206 is defined herein as including both volatile andnonvolatile memory and data storage components. Volatile components arethose that do not retain data values upon loss of power. Nonvolatilecomponents are those that retain data upon a loss of power. Thus, thememory 1206 may comprise, for example, random access memory (RAM),read-only memory (ROM), hard disk drives, solid-state drives, USB flashdrives, memory cards accessed via a memory card reader, floppy disksaccessed via an associated floppy disk drive, optical discs accessed viaan optical disc drive, magnetic tapes accessed via an appropriate tapedrive, and/or other memory components, or a combination of any two ormore of these memory components. In addition, the RAM may comprise, forexample, static random access memory (SRAM), dynamic random accessmemory (DRAM), or magnetic random access memory (MRAM) and other suchdevices. The ROM may comprise, for example, a programmable read-onlymemory (PROM), an erasable programmable read-only memory (EPROM), anelectrically erasable programmable read-only memory (EEPROM), or otherlike memory device.

Also, the processor 1203 may represent multiple processors 1203 and/ormultiple processor cores and the memory 1206 may represent multiplememories 1206 that operate in parallel processing circuits,respectively. In such a case, the local interface 1209 may be anappropriate network that facilitates communication between any two ofthe multiple processors 1203, between any processor 1203 and any of thememories 1206, or between any two of the memories 1206, etc. The localinterface 1209 may comprise additional systems designed to coordinatethis communication, including, for example, performing load balancing.The processor 1203 may be of electrical or of some other availableconstruction.

Although the gantry system control application 927 and other varioussystems described herein may be embodied in software or code executed bygeneral purpose hardware as discussed above, as an alternative the samemay also be embodied in dedicated hardware or a combination ofsoftware/general purpose hardware and dedicated hardware. If embodied indedicated hardware, each can be implemented as a circuit or statemachine that employs any one of or a combination of a number oftechnologies. These technologies may include, but are not limited to,discrete logic circuits having logic gates for implementing variouslogic functions upon an application of one or more data signals,application specific integrated circuits (ASICs) having appropriatelogic gates, field-programmable gate arrays (FPGAs), or othercomponents, etc. Such technologies are generally well known by thoseskilled in the art and, consequently, are not described in detailherein.

The flowcharts of FIGS. 10 and 11 show the functionality and operationof an implementation of portions of the gantry system 1000 and/or thegantry system control application 927. If embodied in software, eachblock may represent a module, segment, or portion of code that comprisesprogram instructions to implement the specified logical function(s). Theprogram instructions may be embodied in the form of source code thatcomprises human-readable statements written in a programming language ormachine code that comprises numerical instructions recognizable by asuitable execution system such as a processor 1203 in a computer systemor other system. The machine code may be converted from the source code,etc. If embodied in hardware, each block may represent a circuit or anumber of interconnected circuits to implement the specified logicalfunction(s).

Although the flowcharts of FIGS. 10 and 11 show a specific order ofexecution, it is understood that the order of execution may differ fromthat which is depicted. For example, the order of execution of two ormore blocks may be scrambled relative to the order shown. Also, two ormore blocks shown in succession in FIGS. 10 and 11 may be executedconcurrently or with partial concurrence. Further, in some embodiments,one or more of the blocks shown in FIGS. 10 and 11 may be skipped oromitted. In addition, any number of counters, state variables, warningsemaphores, or messages might be added to the logical flow describedherein, for purposes of enhanced utility, accounting, performancemeasurement, or providing troubleshooting aids, etc. It is understoodthat all such variations are within the scope of the present disclosure.

Also, any logic or application described herein, including the gantrysystem control application 927, that comprises software or code can beembodied in any non-transitory computer-readable medium for use by or inconnection with an instruction execution system such as, for example, aprocessor 1203 in a computer system or other system. In this sense, thelogic may comprise, for example, statements including instructions anddeclarations that can be fetched from the computer-readable medium andexecuted by the instruction execution system. In the context of thepresent disclosure, a “computer-readable medium” can be any medium thatcan contain, store, or maintain the logic or application describedherein for use by or in connection with the instruction executionsystem.

The computer-readable medium can comprise any one of many physical mediasuch as, for example, magnetic, optical, or semiconductor media. Morespecific examples of a suitable computer-readable medium would include,but are not limited to, magnetic tapes, magnetic floppy diskettes,magnetic hard drives, memory cards, solid-state drives, USB flashdrives, or optical discs. Also, the computer-readable medium may be arandom access memory (RAM) including, for example, static random accessmemory (SRAM) and dynamic random access memory (DRAM), or magneticrandom access memory (MRAM). In addition, the computer-readable mediummay be a read-only memory (ROM), a programmable read-only memory (PROM),an erasable programmable read-only memory (EPROM), an electricallyerasable programmable read-only memory (EEPROM), or other type of memorydevice.

Further, any logic or application described herein, including the gantrysystem control application 927, may be implemented and structured in avariety of ways. For example, one or more applications described may beimplemented as modules or components of a single application. Further,one or more applications described herein may be executed in shared orseparate computing devices or a combination thereof. For example, aplurality of the applications described herein may execute in the samecomputing device 1200, or in multiple computing devices 1200 in the samecomputing environment 903.

Disjunctive language such as the phrase “at least one of X, Y, or Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to present that an item, term, etc., may beeither X, Y, or Z, or any combination thereof (e.g., X, Y, and/or Z).Thus, such disjunctive language is not generally intended to, and shouldnot, imply that certain embodiments require at least one of X, at leastone of Y, or at least one of Z to each be present.

Embodiments of the present disclosure may be described by the followingclauses:

Clause 1. A system, comprising: a recirculating track having a lower runand an upper run spaced vertically from each other; a plurality ofconveyors in parallel and at least partially disposed beneath the track;a plurality of stowage locations in parallel and disposed at leastpartially beneath the track, the stowage locations being spaced from theconveyors in a first direction; a plurality of gantries supported formovement along the track in the first direction and spanning a width ofthe plurality of conveyors and the plurality of stowage locations; and arespective plurality of actuators disposed on individual ones of theplurality of gantries and operable to retrieve a plurality of items fromthe conveyors and deposit the items to respective stowage locations asthe individual ones of the plurality of gantries move along the track inthe first direction over the plurality of conveyors and the plurality ofstorage locations, wherein the gantries are operable to recirculate fromthe stowage locations to the conveyors by continuing to move in thefirst direction along the track so that the gantries return in a seconddirection opposite of the first direction.

Clause 2. The system of clause 1, wherein each actuator is configured tomove laterally on a corresponding gantry in order to access at least twoof the plurality of stowage locations.

Clause 3. The system of clauses 1 to 2, wherein each gantry and therespective plurality of actuators vertically inverts while returning tothe plurality of conveyors on the track.

Clause 4. A system, comprising: a track including a lower run and anupper run spaced vertically from each other, the track being disposed atleast partially above a picking area comprising plural side-by-sidepicking locations and at least partially above a stowage area comprisingplural side-by-side stowage locations spaced from the picking locationsin a first direction; a gantry supported for movement along the track inthe first direction and spanning the picking area and the stowage area;at least one actuator disposed on the gantry and operable to retrieve anitem from one of the picking locations and deposit the item in one ofthe stowage locations as the gantry moves along the track in the firstdirection over the picking area and the stowage area; and wherein thegantry is operable to vertically recirculate from the stowage area tothe picking area by continuing to move in the first direction along thetrack so that the gantry returns in a second direction opposite to thefirst direction.

Clause 5. The system of clause 4, further comprising: at least onecomputing device; and instructions executable in the at least onecomputing device, wherein when executed the instructions cause the atleast one computing device to at least: receive an identifier of aparticular item from a scanner; determine a particular stowage locationof the stowage locations based at least in part on the identifier; andcause the at least one actuator to deposit the particular item in theparticular stowage location.

Clause 6. The system of clauses 4 to 5, further comprising: at least onecomputing device; and instructions executable in the at least onecomputing device, wherein when executed the instructions cause the atleast one computing device to at least: determine that a capacitythreshold for a first storage unit at a particular stowage location ofthe stowage locations is met; cause a first robotic drive unit to movethe first storage unit out of the particular stowage location; and causea second robotic drive unit to move a second storage unit to theparticular stowage location.

Clause 7. The system of clauses 4 to 6, wherein at least two of thestowage locations are arranged in line in the first direction with aparticular picking location of the picking locations.

Clause 8. The system of clauses 4 to 7, wherein at least one of thestowage locations comprises a gaylord disposed on top of a pallet.

Clause 9. The system of clause 8, wherein the pallet rests upon a podconfigured to accommodate a robotic drive unit.

Clause 10. The system of clauses 4 to 9, further comprising a respectiverobot configured to orient items on a particular picking location of thepicking locations in order to be retrieved by a particular actuator ofthe at least one actuator.

Clause 11. The system of clauses 4 to 10, wherein the at least oneactuator is configured to move laterally along the gantry.

Clause 12. The system of clauses 4 to 11, wherein the at least oneactuator is configured to perform vertically telescoping movement.

Clause 13. The system of clauses 4 to 12, wherein the at least oneactuator is configured to retain the item via a vacuum applied by apneumatic pad.

Clause 14. The system of clauses 4 to 13, wherein the gantry furthercomprises a plurality of gantries, and a respective plurality ofactuators is disposed on individual ones of the plurality of gantries.

Clause 15. The system of clauses 4 to 14, wherein the picking locationsare respective conveyors.

Clause 16. A method, comprising: retrieving a plurality of items from aplurality of side-by-side picking locations via a plurality of actuatorsdisposed on a gantry spanning a width of the picking locations; movingthe gantry along a track in a first direction toward a plurality ofside-by-side stowage locations, the plurality of stowage locations beingspaced from the plurality of picking locations in the first direction,wherein the track has a lower run and an upper run spaced verticallyfrom each other; and depositing individual ones of the plurality ofitems in respective ones of the plurality of stowage locations via theplurality of actuators as the gantry moves over the plurality of stowagelocations.

Clause 17. The method of clause 16, further comprising moving the gantryalong the track in the first direction to return to the plurality ofpicking locations.

Clause 18. The method of clause 17, wherein the gantry and the pluralityof actuators vertically invert while moving to return to the pluralityof picking locations.

Clause 19. The method of clauses 16 to 18, further comprising:determining that a capacity threshold is met for a first item storageunit at a particular stowage location of the plurality of stowagelocations; moving, via a first robotic drive unit, the first itemstorage unit out from the particular stowage location; and moving, via asecond robotic drive unit, a second item storage unit into theparticular stowage location.

Clause 20. The method of clauses 16 to 19, further comprising: scanningan identifier on a particular item of the plurality of items; anddetermining a particular stowage location into which the item is to bedeposited based at least in part on the identifier.

Clause 21. A system, comprising: a horizontally oriented recirculatingtrack; a first picking area defining a first plurality of pickinglocations and a second picking area defining a second plurality ofpicking locations; a plurality of gantries spanning the first pluralityof picking locations or the second plurality of picking locations andsupported for movement along the track; a plurality of actuatorssupported on each of the plurality of gantries; a first stowage areadefining a first plurality of side-by-side stowage locations disposed atleast partially beneath the track and spaced from the first plurality ofpicking locations in a direction of movement of the plurality ofgantries along the track; a second stowage area defining a secondplurality of side-by-side stowage locations disposed at least partiallybeneath the track and spaced from the second plurality of pickinglocations in the direction of movement of the plurality of gantriesalong the track; and wherein, when operated, each plurality of actuatorsindividually retrieves a first plurality of items from the firstplurality of picking locations and then deposits individual ones of thefirst plurality of items in respective ones of the first plurality ofstowage locations as a corresponding one of the plurality of gantriesmoves along the track over the respective ones of the first plurality ofstowage locations, and subsequently, each plurality of actuatorsindividually retrieves a second plurality of items from the secondplurality of picking locations and then deposits individual ones of thesecond plurality of items in respective ones of the second plurality ofstowage locations as the corresponding one of the plurality of gantriesmoves along the track over the respective ones of the second pluralityof stowage locations.

Clause 22. The system of clause 21, wherein the picking locationscorrespond to a plurality of conveyors.

Clause 23. The system of clauses 21 to 22, wherein each of the pickinglocations has a respective robot configured to orient items forretrieval by a respective actuator.

Clause 24. A system, comprising: a horizontally oriented track includinga first segment extending in a first direction, the track being disposedat least partially above a picking area comprising plural side-by-sidepicking locations and at least partially above a stowage area comprisingside-by-side stowage locations spaced from the picking locations in thefirst direction; a gantry supported for movement on the track andspanning the picking and stowage locations; a plurality of actuatorsdisposed on the gantry and operable to retrieve an item from one of thepicking locations and deposit the item in one of the stowage locationsas the gantry moves along the track in the first direction over thepicking area and the stowage area; and wherein the gantry is operable torecirculate from the stowage area to the picking area by continuing tomove in the first direction along the track so that the gantry returnsin a second direction opposite to the first direction.

Clause 25. The system of clause 24, wherein the gantry is centered onthe horizontally oriented track.

Clause 26. The system of clauses 24 to 25, wherein the horizontallyoriented track is a rollercoaster-style oval track.

Clause 27. The system of clauses 24 to 26, wherein each of the stowagelocations is arranged in line in the first direction with a particularpicking location of the picking locations.

Clause 28. The system of clauses 24 to 27, wherein individual ones ofthe plurality of actuators are configured to perform verticallytelescoping movement.

Clause 29. The system of clauses 24 to 28, wherein individual ones ofthe plurality of actuators are configured to move laterally along thegantry.

Clause 30. The system of clauses 24 to 29, further comprising: at leastone computing device; and instructions executable in the at least onecomputing device, wherein when executed the instructions cause the atleast one computing device to at least: receive an identifier of theitem from a scanner; determine a particular stowage location of thestowage locations based at least in part on the identifier; and cause acorresponding actuator of the plurality of actuators to deposit the itemin the particular stowage location.

Clause 31. The system of clause 30, wherein the scanner comprises atleast one of: a radio-frequency identifier scanner or a barcode scanner.

Clause 32. A method, comprising: retrieving a plurality of items from aplurality of side-by-side picking locations via a plurality of actuatorsdisposed on a gantry spanning a width of the plurality of pickinglocations; moving the gantry along a track in a first direction toward aplurality of side-by-side stowage locations, the gantry being centeredon the track, the plurality of stowage locations being spaced from theplurality of picking locations in the first direction; and depositingindividual ones of the plurality of items in respective ones of theplurality of stowage locations via the plurality of actuators as thegantry moves over the plurality of stowage locations.

Clause 33. The method of clause 32, wherein depositing the individualones of the plurality of items in the respective ones of the stowagelocations via the plurality of actuators further comprises placing anitem within a gaylord disposed on top of a pallet.

Clause 34. The method of clauses 32 to 33, wherein the track has a lowerrun and an upper run that are spaced vertically from each other.

Clause 35. The method of clauses 32 to 34, wherein the track is arollercoaster-style track.

Clause 36. The method of clauses 32 to 35, further comprising, afterdepositing the individual ones of the plurality of items in therespective ones of the plurality of item storage locations, moving thegantry along the track over another plurality of side-by-side pickinglocations.

Clause 37. The method of clause 36, further comprising retrievinganother plurality of items from the other plurality of picking locationsvia the plurality of actuators.

Clause 38. The method of clause 37, further comprising moving the gantryalong the track toward another plurality of side-by-side stowagelocations.

Clause 39. The method of clause 38, further comprising depositingindividual ones of the other plurality of items in respective ones ofthe other plurality of stowage locations via the plurality of actuatorsas the gantry moves over the other plurality of stowage locations.

Clause 40. The method of clause 39, further comprising, after depositingthe individual ones of the other plurality of items in the respectiveones of the other plurality of stowage locations, moving the gantryalong the track in the first direction to recirculate to the pluralityof picking locations.

It should be emphasized that the above-described embodiments of thepresent disclosure are merely possible examples of implementations setforth for a clear understanding of the principles of the disclosure.Many variations and modifications may be made to the above-describedembodiment(s) without departing substantially from the spirit andprinciples of the disclosure. All such modifications and variations areintended to be included herein within the scope of this disclosure andprotected by the following claims.

Therefore, the following is claimed:
 1. A system, comprising: arecirculating track having a lower run and an upper run spacedvertically from each other; a plurality of conveyors in parallel and atleast partially disposed beneath the track; a plurality of stowagelocations in parallel and disposed at least partially beneath the track,the stowage locations being spaced from the conveyors in a firstdirection; a plurality of gantries supported for movement along thetrack in the first direction and spanning a width of the plurality ofconveyors and the plurality of stowage locations; and a respectiveplurality of actuators disposed on individual ones of the plurality ofgantries and operable to retrieve a plurality of items from theconveyors and deposit the items to respective stowage locations as theindividual ones of the plurality of gantries move along the track in thefirst direction over the plurality of conveyors and the plurality ofstorage locations, wherein the gantries are operable to recirculate fromthe stowage locations to the conveyors by continuing to move in thefirst direction along the track so that the gantries return in a seconddirection opposite of the first direction.
 2. The system of claim 1,wherein each actuator is configured to move laterally on a correspondinggantry in order to access at least two of the plurality of stowagelocations.
 3. The system of claim 1, wherein each gantry and therespective plurality of actuators vertically inverts while returning tothe plurality of conveyors on the track.
 4. A system, comprising: atrack including a lower run and an upper run spaced vertically from eachother, the track being disposed at least partially above a picking areacomprising plural side-by-side picking locations and at least partiallyabove a stowage area comprising plural side-by-side stowage locationsspaced from the picking locations in a first direction; a gantrysupported for movement along the track in the first direction andspanning the picking area and the stowage area; at least one actuatordisposed on the gantry and operable to retrieve an item from one of thepicking locations and deposit the item in one of the stowage locationsas the gantry moves along the track in the first direction over thepicking area and the stowage area; and wherein the gantry is operable tovertically recirculate from the stowage area to the picking area bycontinuing to move in the first direction along the track so that thegantry returns in a second direction opposite to the first direction. 5.The system of claim 4, further comprising: at least one computingdevice; and instructions executable in the at least one computingdevice, wherein when executed the instructions cause the at least onecomputing device to at least: receive an identifier of a particular itemfrom a scanner; determine a particular stowage location of the stowagelocations based at least in part on the identifier; and cause the atleast one actuator to deposit the particular item in the particularstowage location.
 6. The system of claim 4, further comprising: at leastone computing device; and instructions executable in the at least onecomputing device, wherein when executed the instructions cause the atleast one computing device to at least: determine that a capacitythreshold for a first storage unit at a particular stowage location ofthe stowage locations is met; cause a first robotic drive unit to movethe first storage unit out of the particular stowage location; and causea second robotic drive unit to move a second storage unit to theparticular stowage location.
 7. The system of claim 4, wherein at leasttwo of the stowage locations are arranged in line in the first directionwith a particular picking location of the picking locations.
 8. Thesystem of claim 4, wherein at least one of the stowage locationscomprises a gaylord disposed on top of a pallet.
 9. The system of claim8, wherein the pallet rests upon a pod configured to accommodate arobotic drive unit.
 10. The system of claim 4, further comprising arespective robot configured to orient items on a particular pickinglocation of the picking locations in order to be retrieved by aparticular actuator of the at least one actuator.
 11. The system ofclaim 4, wherein the at least one actuator is configured to movelaterally along the gantry.
 12. The system of claim 4, wherein the atleast one actuator is configured to perform vertically telescopingmovement.
 13. The system of claim 4, wherein the at least one actuatoris configured to retain the item via a vacuum applied by a pneumaticpad.
 14. The system of claim 4, wherein the gantry further comprises aplurality of gantries, and a respective plurality of actuators isdisposed on individual ones of the plurality of gantries.
 15. The systemof claim 4, wherein the picking locations are respective conveyors. 16.A method, comprising: retrieving a plurality of items from a pluralityof side-by-side picking locations via a plurality of actuators disposedon a gantry spanning a width of the picking locations; moving the gantryalong a track in a first direction toward a plurality of side-by-sidestowage locations, the plurality of stowage locations being spaced fromthe plurality of picking locations in the first direction, wherein thetrack has a lower run and an upper run spaced vertically from eachother; and depositing individual ones of the plurality of items inrespective ones of the plurality of stowage locations via the pluralityof actuators as the gantry moves over the plurality of stowagelocations.
 17. The method of claim 16, further comprising moving thegantry along the track in the first direction to return to the pluralityof picking locations.
 18. The method of claim 17, wherein the gantry andthe plurality of actuators vertically invert while moving to return tothe plurality of picking locations.
 19. The method of claim 16, furthercomprising: determining that a capacity threshold is met for a firstitem storage unit at a particular stowage location of the plurality ofstowage locations; moving, via a first robotic drive unit, the firstitem storage unit out from the particular stowage location; and moving,via a second robotic drive unit, a second item storage unit into theparticular stowage location.
 20. The method of claim 16, furthercomprising: scanning an identifier on a particular item of the pluralityof items; and determining a particular stowage location into which theitem is to be deposited based at least in part on the identifier.